The subject matter of this disclosure relates generally to electrical machines, and more particularly, to a control method for reducing torque ripple in electrical machines.
A limiting factor in the application of electrical machines (e.g., switched reluctance motors (SRMs), flux switching motors (FSMs), or wound-field synchronous motors) is the torque ripple produced by interaction of the stator and rotor magnetic fields as the machine rotates. (While all electrical machines have this issue, aspects of this invention relate to those machines in which there is a winding that is excited with nominal DC current). In the past, it was possible to reduce torque ripple produced by the electrical machine only over a limited speed range and with the use of sophisticated current regulators applied to the armature currents.
Control of the electrical machine is complicated by the spatial and magnetic nonlinearities inherent to the machine. The traditional approach to electrical machine excitation is to design the current waveform for each phase, and implement those current waveforms independently of one another. This requires an inverter structure that is different from the inverter structure that is used for other types of AC machines, such as permanent magnet synchronous and induction machines.
In view of the foregoing, there is a need for a method of reducing torque ripple in electrical machines that facilitates the use of a standard inverter topology, combined with a simpler current regulation algorithm.